Recordings can be made to most commonly available media including digital recorder, minidisc, tape, and DAT. The recording device should ideally have a 'line in' socket to ensure the quality of the recording. Recording via a 'mic' socket may result in corrupted recordings so it is important ot check the compatibility of a recorder with your detector before purchasing a recording device.

If you simply want to make recordings of bat calls for playing back from a recording device, a heterodyne detector with a tape socket is all you need. The majority of detectors have a 3.5mm tape output socket so all that is required is a stereo lead with a 3.5mm male jack on one end and a jack suitable for the recording device at the other. Most portable recorders use a 3.5mm jack.

A sonogram is a graph of sound frequency against time. The sonogram can tell you a lot about the nature of the bat call including the highest frequency, lowest frequency and peak frequency. You can determine the bandwidth, duration and time interval between calls. All bat calls can be described as CF (constant frequency), FM (frequency modulating) or a combination of the two.

Bat calls for computer analysis must be made with a freqency division or time expansion detector. Time expansion detectors produce the highest quality sonograms. Recordings are made in the conventional manner to a recorder and then converted into a sound file in a format (eg .wav) by your PC sound card and analysis program. If you wish to transfer your recording to a PC for analysis then your PC must have a soundcard with a 'line in ' socket. Some laptop PC's combine the 'line in' with the 'mic' socket. In these cases it is possible to make the connection using the 'mic' socket.

You must make sure your windows settings are correct on your PC for your sound analysis program to detect the recording. Select Windows volume control, choose options and then the properties window. Select the recording button and look in 'Show the following volume controls window'. Ensure that the LINE box is checked and then click OK.

It should now be possible to click the 'record' button in your sound analysis program and start recording the bat call from your recording device.

Some bat detectors are suitable for leaving out in the field with a recording device to make recordings automatically.

The simplest way of setting up a remote recording device is to place a voice activated recorder next to the bat detector speaker. When a bat call is detected the tape recorder will be triggered by the speaker output. The disadvantage of this method is that recording quality can be poor particularly if the bat was some distance away from the detector. There may also be false triggering from other background noise. This method can be used with any heterodyne, frequency division and time expansion detectors with a speaker.

The Pettersson D240x detector can be connected to an optional relay unit which in turn can be connected to a suitable recorder. The 240x will automatically trigger the relay when a bat call is detected.

The Pettersson D500X detector is also designed for remote recording. It will take up to 4 CF cards and can be left to record in the field for up to 2 weeks.